To ensure safety while maintaining efficient operation and fast power regulation, this paper proposes a coordinated control strategy for variable-speed pumped storage units with full-size converters (FSC-VSPSU) in generation state. First, the dynamic stability characteristics and the key influencing factors in the fast power control mode and fast speed control mode are analyzed using the eigenvalue analysis method. The results indicate that the fast speed control mode can effectively address the issue of ultra-low frequency oscillation induced by fast power control. Then, the characteristics among the optimal speed, guide vane opening, and efficiency are clarified through laboratory testing of a pump turbine model machine, laying the foundations for developing optimized operation for the pumped storage units. Based on the analysis of slow load regulation and power step regulation, the power frequency regulation characteristics of the two control modes are revealed. Finally, leveraging the advantages of dynamic stability and power-speed regulation ability under the two control modes, a novel coordinated control strategy is proposed. The strategy has been applied to the first FSC-VSPSU in China, and the field tests demonstrate that the unit achieves excellent speed regulation performance and fast power regulation capability.